Camera Mapping is certainly a useful option. In regards to modeling for your scene and in addition to using camera mapping in your scene, it's good to create textures specific to objects in your scene. Objects such as vehicles, aircraft and other moving objects that may show more than one side need properly fitted textures.

OK dentsinger, so I need Bodypaint... yep... This little article/ tutorial is pretty useful, thanx again.
Indeed, I could use camera mapping but it would be more complicated than it's needed: I just want to find the good size to create my texture comps! Moreover there is no cam movement in my scene, it's totally still.

A good rule of thumb is to paint twice as big as your final output.
so for a theatrical render, 1920 x 1080, around 4K should do it. I also try to keep it the exact power of two for better sampling. So in this case,
3840 x 2160 but the bigger the better. I've done up to 7k... For bigger I have to split my PSD file into multiple doc. :(

And for characters or UV mapped models, 4~5K is pretty good. It might jam your render farm but if you have a render engine that allows tiles, (RenderMan*) you should be fine even with 8K.

But maybe I didn't get your question. Anyways, you guys let me know...